COMPOSITION PROFILING OF GRADED DIELECTRIC FUNCTION MATERIALS BY SPECTROSCOPIC ELLIPSOMETRY

In this work, the characterization of graded composition layers in tra nsparent materials by spectroscopic ellipsometry (SE) is described. Th e sensitivity limits were modeled by comparing calculated spectra for samples with and without diffusion profiles at the sample surface for several glass compositions. It was found that for known index profile shapes, the depth sensitivity can be quite high. The sensitivity of th e technique increases as the diffusion depth and refractive index cont rast increases. The accuracy of the thickness determination depends on the total thickness of the graded layer; for a given system, the accu racy of the composition measurements did not depend on the surface con centration. Leached alkali-aluminosilicate and modified lead silicate glasses were examined by SE to experimentally confirm the modeling pre dictions on the composition depth profiling. Extremely good correlatio n between the SE-determined depth profile and SIMS measurements on sim ilar samples was obtained for the case of the modified lead silicate g lass. For the aluminosilicate glass, simultaneous roughening of the gl ass surface during etching makes composition profiling more difficult. (C) 1998 Elsevier Science S.A.